1. Field of the Invention
The present invention relates to a navigation device which is mounted in a moving body and which guides a route from a present position to a destination.
2. Description of Related Art
Navigation devices which guide a route from a current position of an automobile to a destination while driving have been widely applied. In this type of navigation device, when a destination is set by a user, the device searches a preferred route from the current position to the destination. When the searched route is presented to a user, it is common to present the route in an xe2x80x9centire route formatxe2x80x9d in which a route from a geographical position, at which a destination is set, to the destination is displayed on the same screen by switching a map scale. Furthermore, a method is employed of displaying more detailed information about the route by scrolling the map display automatically or manually along the route by switching to a detailed map display with a large map scale ratio. In addition, a method of sequential display of guiding maps of intersections on the route forward of a current position, or a method of displaying the route schematically by main branching points on the display device are also known in the art. Furthermore, it is possible to execute the guiding operation by use of voice commands.
FIG. 1 is a block diagram showing a first conventional navigation device as disclosed in JP-A-5-297800. In the figure, reference numeral 1 denotes a touch switch for inputting a destination or the like, 2 is a vehicle speed sensor for detecting a vehicle speed, 3 is a bearing sensor for detecting a bearing, 4 is an external storage device for storing information displaying classes of roads connecting branching points or information displaying classes of branching point of roads and pre-stored map information data. 5 is a display device for displaying information regarding main points such as branching points which are on a route from the present position to the destination. 6 is a control device which searches a travel route of the vehicle based on an input signal from the bearing sensor 3 and the vehicle sensor 2 and an input signal from the switch 1 and which displays main branching points on the travel route in summary form on the display device 5.
The operation of the first conventional navigation device will be described below.
Firstly, route searching is executed. The route searching is executed according to a Dijkstra method. Of the routes connecting the present position and the destination, the device searches a route passing along main roads in which there are few right or left turns and in which the names of intersections at which turns are made are known. The search is made on the basis of the map information data stored in the external storage device 4.
After the route is searched, the number of nodes contained on the route is counted and it is determined whether the number of nodes is less than or equal to 10. When the number of nodes is less than or equal to 10, the display process is executed to display the searched route.
On the other hand, when there are more than 10 nodes, a summarizing process is applied to the nodes contained on the route in which they are summarized based on informational value of each node. The summarizing process entails deleting those nodes of low information value until the number of nodes contained on the route are less than or equal to 10. Thereafter, display processing is executed. Herein information value is a product of a turning coefficient, a name presence/absence coefficient and a node category coefficient. The node category coefficient is a fixed coefficient corresponding to categories of nodes such as expressway entrance/exit, tollway entrance/exit or national road intersection. The node name presence/absence coefficient is a fixed coefficient which corresponds to the presence or absence of a name of the node. The turning coefficient is a fixed coefficient which corresponds to the presence or absence of left or right turns.
In the display process, the name of the destination and present position, the name of main branching points on the route from the present position to the destination, the distance between each branching point, representative place names which indicate the direction of travel, and the names of roads which should be taken at branching points are displayed on the display device 5.
FIG. 2 is a block diagram of a second conventional navigation device as disclosed in International Publication WO98/51995. In the figure, reference numeral 10 denotes a control means which performs control of the overall device and each type of calculation in the navigation device. 11 is a map information storage means which stores digitized map information data such as intersection data, road data and the like. 12 is a present position detection means which detects a present position of the moving body in which the navigation device is mounted.
13 is a route setting means which sets a route between two points on a map on the basis of map information data stored in the map information storage means 11. 14 is a guide object intersection detection means which detects a guide object intersection to be guided on the route set by the route setting means 13. 15 is a quantizing calculation means which quantizes the route of the moving body onto a schematic map displaying the characteristic features of the route.
16 is a display means which displays a route quantized by the quantizing calculation means with respect to a guide object intersection detected by the guide object intersection detection means 14. 17 is a voice guide message generation means having a voice information storage means (not shown) which stores necessary words or phrases for guide messages as voice wave form data. The voice guide message generation means selects voice wave form data such as words or phrases for guide messages and generates such combinations as guide messages when a quantized route of the moving body is displayed on the display means 16. 18 is a voice output means which notifies a user by voice commands of guide messages generated by the voice guide message generation means.
The operation of the second conventional navigation device will be described below.
FIG. 3 is a flowchart explaining the operation of the second conventional navigation device shown in FIG. 2.
Firstly, in a step ST1, the route setting means 13 sets two points on the map on the basis of latitude and longitude from the map information data read from the map information storage means 11 and then sets a route between the two points using a general search algorithm on a network such as a Dijkstra method or the like.
Then, in a step ST2, the present position detection means 12 detects a present position (C1) of the moving body. In a step ST3, the flags FL1, FL2, FL3 are respectively initialized to 0.
Then, in a step ST4, the guide object intersection detection means 14 extracts an intersection with, for example, more than three roads being connected to the intersection as a forward guide object intersection (C2). The intersection is an intersection on the route set by the route setting means 13 and, of the two geographical points set by the route setting means, the intersection is further forward than present position (C1) detected by the present position detection means 12.
In the step ST5, the detection of the present position (C1) of the moving body is performed again by the present position detection means 12 and in a step ST6, a road distance (L1) between the present position (C1) of the moving body and the forward guide object intersection (C2) is calculated on the basis of map information data read from the map information storage means 11.
Then, in a step ST7, further processing operations are selected in response to this distance (L1).
When the distance (L1) is greater than a predetermined reference distance (L2) (for example 1000 meters), the routine progresses to step ST8 and it is determined whether the flag FL1 has a value of 0 or not. When the value of the flag is 0, in a step ST9, a guide output A which is related to the forward guide object intersection (C2) is executed. The guide output A comprises extracting only the section to the forward guiding object intersection (C2) extracted by the quantizing calculation means 15 of the road on the route on the map. Then, the result is quantized to a simple arrow shape and a display map related to the forward guide object intersection (C2) is displayed on the display means 16. A guide voice message related to the forward guide object intersection (C2) is generated by the voice guide message generation means 17 and the message is reported by voice commands from the voice output means 18. After the execution of the guide output A, in a step ST10, the flag FL1 is varied to a value of 1 and the fact that the guide output A in relation to the forward guide object intersection (C2) has been executed is stored.
Thereafter, in a step ST11, it is determined whether or not the process of setting the route by the route setting means 13 is completed. When it is completed, the guide process is terminated. When it is not completed, the routine returns to a step ST5 and executes the steps of the routine after step ST6.
When the flag FL1 does not have a value of 0 in step ST8, since the guide output A has already been executed, the routine returns to a step ST5.
In a step ST7, when the distance (L1) is less than or equal to the reference value (L2) and greater than the predetermined reference value (L3) (for example 300 meters), the routine progresses to a step ST12, and it is determined whether or not the flag FL2 has a value of 0. When the flag FL2 has a value of 0, in the step ST13, a guide output B related to the forward guide object intersection (C2) is executed. The guide output B comprises extracting only the route section connecting the forward guiding object intersection (C2) of the road on the map extracted by the quantizing calculation means 15. Then, the result is quantized to a simple arrow shape and a display map related to the forward guide object intersection (C2) is displayed on the display means 16. A guide voice message related to the forward guide object intersection (C2) is generated by the voice guide message generation means 17 and the message is reported by voice commands from the voice output means 18. After the execution of the guide output B, in a step ST14, the flag FL2 is varied to a value of 1 and the fact that the guide output B in relation to the forward guide object intersection (C2) has been executed is stored.
Thereafter, in a step ST11, it is determined whether or not the process of setting the route by the route setting means 13 is completed. When it is completed, the guide process is terminated. When it is not completed, the routine returns to a step ST5 and executes the steps of the routine after step ST6.
When the flag FL2 does not have a value of 0 in step ST12, since the guide output has already been executed, the routine returns to a step ST5.
When, in a step ST7, the distance (L1) has a value less than the reference value (L3), the routine progresses to a step ST15 and it is determined whether or not the flag FL3 has a value of 0 or not. When the value of the flag is 0, in a step ST16, the guide output C related to the forward guide object intersection (C2) is executed. The guide output C comprises extracting the present position of the moving body, roads other than roads on the route, route roads connected to the forward guiding object intersection (C2) and the forward guiding object intersection (C2) extracted by the quantizing calculation means 15 on the map. Then, the result is quantized to a simple arrow shape and a display map related to the forward guide object intersection (C2) is displayed on the display means 16. A guide voice message related to the forward guide object intersection (C2) is generated by the voice guide message generation means 17 and the message is reported by voice commands from the voice output means 18. After the execution of the guide output C, in a step ST17, the flag FL3 is varied to a value of 1 and the fact that the guide output C in relation to the forward guide object intersection (C2) has been executed is stored.
Thereafter, in a step ST11, it is determined whether or not the process of setting the route by the route setting means 13 is completed. When it is completed, the guide process is terminated. When it is not completed, the routine returns to a step ST5 and executes the steps of the routine after step ST6.
When the flag FL3 does not have a value of 0 in step ST15, since the guide output C has already been executed, the routine returns to a step ST3, and the flags FL1, FL2, FL3 are initialized to 0. In a step ST4, the forward guide object intersection (C2) is extracted.
Since the conventional navigation device is constructed as above, the problem has arisen that safe operation of the vehicle can be affected as it is necessary for a user to monitor the guide display even when display nodes are displayed in summary form by a summarizing process. Furthermore, the number of guiding nodes provided to guide the entire route by voice commands increases and the problem has arisen that nodes can not be adapted to guide the entire route appropriately in a short time.
Furthermore, when the number of guide nodes is reduced to a predetermined number of summarized nodes in a convention navigation device, the problem has arisen that it is difficult to make guide nodes correspond to a predetermined number of nodes when a plurality of nodes with the same informational value exists.
The present invention is proposed to solve the above problems and has the object of providing a navigation device adapted to store the level of importance of nodes and links and select nodes and links on the searched route based on the level of importance or time for playing voice information. In the navigation device, a voice guide message is generated corresponding to the selected nodes and links and guiding of the route is executed by the voice guide message. Thus, it is possible to guide an entire route appropriately in a short time by voice commands.
The present invention has the further object of providing a navigation device in which when a plurality of nodes and links with the same importance exists and the number of such nodes and links is not equal to a predetermined reference number, nodes and links in proximity to the present position, the number of which corresponds with the predetermined reference number, is selected from nodes and links with the same importance, thereby to make the number of guide nodes and the like accurately correspond with the predetermined reference number.
A navigation device of the present invention is adapted to store a level of importance of each node and link as a part of map information in a map information storage means, to select the nodes and links on the searched route based on the level of importance and to generate a voice guide message corresponding to the selected links and nodes. In this way, it is possible to guide an entire route appropriately in a short period of time by voice commands.
The navigation device of the present invention may be adapted to select the nodes and links on the searched route in such a manner that the level of importance of the selected nodes and links is less than or equal to a predetermined reference level and the number of the selected nodes and links is less than or equal to a predetermined reference number, and to generate a voice guide message corresponding to the selected nodes and links. In such a way, even when the number of nodes and links with a high level of importance is less than a predetermined reference number, the voice guiding with respect to the nodes and links having low level of importance is not executed. Thus, it is possible to guide the entire route appropriately.
The navigation device of the present invention may be adapted to delete nodes and links, which are located in proximity to the guide point, from the nodes and links having the same level of importance and to make the number of the selected nodes and links equal to a predetermined reference number, when there exists a plurality of nodes and links with the same level of importance and the number of the selected nodes and links is not equal to the predetermined reference number. In this way, it is possible to make the number of nodes and links to be guided correspond accurately with the predetermined reference number.
The navigation device of the present invention may be provided with a reference value setting means for setting a predetermined reference value and a reference number setting means for setting a predetermined reference number. In this way, it is possible to provide a voice guide with the desired amount and level of importance.
The navigation device of the present invention may be adapted to store information about voice playing times relating to names of each link and node as a part of map information in the map information storage means, to select the nodes and links on the searched route in order of highest importance in such a manner that the voice playing time for the voice guide message is less than or equal to a predetermined reference value, and to generate the voice guide message corresponding to the selected nodes and links. In such a way, it is possible to accurately make the time taken for voice guiding under a predetermined reference value.